The boy put a hand to his chin. He was of the opinion that it made him look more serious. "In theory it should be possible. If the device is made to receive a certain signal it could be made to receive others, or the one it's set to pick up could be found.."

He shrugged. "The problem would be rigging one device strong enough to send out a signal to the others. And they'd have to have theirs on and tuned to the right place. I don't know how the man on the radio works them so they switch on automatically, but that would be beyond difficult."